Development of non-metallic (e.g., amalgam-substitute) restorative materials is a high research priority due to environmental concerns associated with metals waste and disposal. Ceramics are an intriguing candidate for replacing metal-based restorative materials. Ceramics in dental applications provide excellent chemical durability, wear resistance, biocompatibility, environmental friendliness, and esthetics. However, widespread all-ceramic restoration use has been hindered by concerns related to marginal fracture resistance and clinical longevity. Previous studies (Kelly et al., 1989; Thompson et al., 1994) found that clinical fracture of all-ceramic restorations initiated along internal surfaces (e.g., bonded surfaces) almost exclusively. It is therefore critical to overcome fracture problems if these materials are to gain widespread acceptance. The overall goal of this research is to produce tough, fatigue-resistance ceramic restorations by applying thin film plasma-deposited ceramic surface coatings. Four specific aims are proposed. Aim 1 proposes studies to test the hypothesis that application of sputter deposited thin film coatings will enhance fracture and fatigue resistance of traditional commercial dental ceramic materials by at least 50%. Aim 2 proposes studies to test the hypothesis that sputter deposited thin films with fine-grained (less than 1 um microstructures will yield substrate/thin film constructs with significantly greater fracture toughness than achieved with thin films possessing columnar grain structures. Aim 3 proposes studies to test the hypothesis that presence of sputter deposited thin film ceramic coatings will not adversely affect the interfacial toughness with dental luting cements or the optical characteristics (transmittance, index of refraction, and L*a*b* color parameters) of modified restorations. Aim 4 proposes to test the hypotheses that multilayer and/or compositionally graded thin film surface coatings will yield a substrate/thin film construct with significantly greater fracture toughness than is achieved with unicompositional thin films. Candidate deposition materials include Al2O3, ZrO2, MgAl2O4, AlN, Si3N4, SiC, and diamond-like C. Coatings will be created using RF magnetron sputter deposition. Multilayer and compositionally graded coatings will be created using multiple target and reactive sputter deposition. Fracture toughness will be determined by controlled-flaw fracture strength methods and fractographic evaluation of fracture-initiating flaws. Fatigue behavior will be characterized by developing lifetime prediction profiles. SEM, TEM, and AFM will be used to characterize interfaces and microstructures of deposited thin films.